The present invention relates to an image processing apparatus and an image processing method, and more specifically, to an image processing apparatus and an image processing method, which converts an input image and also generates a control signal used to control an image forming operation every pixel with respect to this input image.
A conspicuous development has been made in high resolution of recent printers. For instance, in electro-photographic type printers, the resolution of 600 dpi could be realized in the main scanning direction, and also the resolution of 600 dpi could be realized in the sub-scanning direction. However, even in such a printer having the above-explained high resolution, there is a shortage of another resolution required to print out characters and line drawings in a smooth manner. As a result, for instance, as disclosed in U.S. Pat. No. 4,847,641 and the Unexamined Japanese Patent Application Publication No. Hei 8-23446, the technique for expanding the resolution (so-called xe2x80x9csmoothing process technique) has been conducted into the electronic-photographic type printer. In this smoothing process technique, the dimension of the pixel to be formed is varied based upon the pattern matching result between the shape of the input image within a block having a certain dimension and the specific pattern. On the other hand, in order to improve the gradation characteristic of photographs/graphics, such a halftone screening operation as the dither processing operation, or the error diffusion process operation has been employed in general-purpose printers.
In documents printed out by printers, there are many possibilities that both photographs/graphics and characters/line drawings are mixed with each other within 1 page. When only the smoothing process operation is carried out with respect to such a document to print these smooth-processed document, the gradation characteristics of the photographs/graphics would be deteriorated. Conversely, when only the area gradation process operation is carried out with respect to such a document, the characters/line drawings could not be printed out in the smooth manner.
To solve this problem, for example, the Unexamined Japanese Patent Application Publication No. Hei 8-139918 describes the method for switching the smoothing process operation and the halftone screening operation based on the comparison result between the pixel value of the input image and the threshold value. Also, the Unexamined Japanese Patent Application Publication No. Hei 7-232463 discloses such a method that the feature is extracted from the data (will be referred to as xe2x80x9cPDL dataxe2x80x9d hereinafter) described by the page description language (will be referred to as a xe2x80x9cPDLxe2x80x9d hereinafter), the input image of 1 page is subdivided into a plurality of regions in accordance with the extracted feature, and then the content of the processing operation for the input image is changed every region. In accordance with this method, for example, the content of the halftone screening operation is varied with respect to each of the regions, and also the smoothing process operation is carried out only for the region of the black character.
However, in the above-explained two smoothing process methods, since the smoothing process operation is carried out based upon the result of the pattern matching operation, even in such an area which is wanted to be processed by the smoothing process operation, if there is no pattern made coincident with this area, then no smoothing process operation is carried out. Conversely, even in such an area which is not wanted to be processed by the smoothing process operation, if there is a pattern made coincident with this area, then the smoothing process operation is carried out.
As a method for capable of solving such a problem, for instance, U.S. Pat. No. 5,455,681 discloses the below-mentioned method. That is, the PDL data is once rasterized by higher resolution than that of the printer, the binary image obtained by rasterizing the PDL data is converted into the multi-valued image having the same resolution as that of the printer, and also, the information indicative of the shift direction of the pixel is added to each of the pixels of the multi-valued image obtained after the conversion. Based on both the multi-valued image and the added information, the printing operation of the pixel is controlled. In accordance with this method, the above-described problem caused by the smoothing process operation by the above-described pattern matching method can be solved, so that the characters and line drawings can be more smoothly printed out. However, this method owns a drawback that when the photographs/graphics are printed by using this print control method, the gradation characteristics thereof would be deteriorated.
The present invention has been made to solve the above-described problems, and therefore, has an object to provide an image processing apparatus and an image processing method, capable of improving image qualities of document images involving various sorts of regions.
To solve the above-described problems, an image processing apparatus, according to the present invention, is featured by comprising: an object tag producing unit for producing an object tag indicative of a sort of an object and also a region of the object contained in an input image represented by an input image data; an image converting unit for converting the input image data to produce converted image data; and a control signal producing unit for inputting thereinto the object tag produced by the object tag producing unit, for selecting any one of the input image data and the converted image data produced by the image converting unit based upon the inputted object tag, and for producing a control signal used to perform an image forming process operation based on the selected image data. As a consequence, the control signal used to perform the image forming process operation is produced based upon the more proper image data selected from the input image data and the converted image data every object contained in the input image. Alternatively, in the above-described arrangement of the image processing apparatus, while a plurality of image converting units may be employed, another control signal used to perform the image forming process operation may be produced based upon the most proper image data selected from a plurality of image converted data and the input image data.
Also, to solve the above-explained problems, an image processing method, according to the present invention, is featured by comprising: an object tag producing step for producing an object tag indicative of a sort of an object and a region of the object contained in an input image expressed by an input image data; an image converting step for converting the input image data to produce at least one converted image data; and a control signal producing step for selecting any one of the input image data and the at least one converted image data produced at the image converting step, and for producing a control signal used to perform an image forming process operation based upon the selected image data. As a consequence, the control signal used to execute the image forming process operation is produced based on the most proper image data selected from the input image data and at least one converted image data every object contained in the input image.